In recent years, demands exist for efficient large-scale cell culturing, tissues, and microorganisms under artificial environments, in fields such as pharmaceutical manufacturing, gene therapy, regenerative medical therapy, and immunotherapy.
In such large-scale cell culturing, especially regarding culturing of floating cells, agitation culturing is commonly practiced using culture vessels equipped with agitating blades. However, agitating blades are not used with cells subject to damage from external force or cells that proliferate while forming aggregates. Instead, a widely employed method is to enclose cells in a culture container where the cells are cultured while being kept stationary (with the cells down at the bottom). Then, in accordance with the degree of proliferation of the cells, the method involves transfer to another culture container with a larger bottom area or increasing the number of containers. Unfortunately, the stationary culturing is problematic in that as the aggregates of cells grow larger with the proliferation of cells, this causes a gradual deficiency of oxygen and nutrients to be fed to the cells, leading to degraded proliferation efficiency.
Additionally, although the transfer to another container involves agitation of a culture solution to cancel the unevenness of oxygen and nutrients, another problem arises in that the handling during the transfer causes damage to the cells, leading to degraded proliferation efficiency.
Meanwhile, shaking culture is also widely practiced to constantly agitate the culture container.
For example, patent document 1 describes a cell culturing apparatus that uses various patterns, such as rotation and shaking, to move a base on which a culture container is placed, thereby agitating a culture solution in the culture container.
Patent document 2 and patent document 3 describe cell culturing apparatuses that shake a liquid culture medium in a culture container while ensuring that no air bubbles occur, and that supply oxygen by motion of waves while ensuring that the cells are not damaged.
With the method of shaking by the cell culturing apparatuses, the entire culture medium is intensely agitated. This causes the cells to be separated from each other and the oxygen and nutrients to be dispersed in the whole area, so that the oxygen and nutrients are supplied sufficiently to each cell.
Additionally, such cell culturing requires the density of cells in the culture solution to be maintained within an appropriate range in accordance with the proliferation of the cells.
That is, an excessively high density of cells in the culture solution prevents a sufficient supply of oxygen and nutrients to each cell, leading to degraded cell proliferation efficiency. Likewise, an excessively low density of cells in the culture solution prevents sufficient securement of cell proliferation efficiency.
In view of this, cell culturing requires a grasp of the density of cells during culturing, by appropriately counting the number of cells in a culture solution in a culture container.
For example, patent document 4 discloses a cell culturing apparatus that properly maintains the density of cells in a culture solution in accordance with the proliferation of cells.
In order to measure the number of cells with such cell culturing apparatus, it is conventional practice to: sample a culture solution containing cultured cells through a sampling port coupled to the interior of the culture container; add a predetermined buffer solution to the sampled culture solution so as to adjust the density of the cells in the sampled culture solution to an appropriate density for measurement; and inject the resulting culture solution into a counter board that indicates the number of the cells. The number of the cells is read by an operator or a machine to calculate the density of the cells.
Patent document 5 discloses a culture apparatus equipped with photographing means. According to this culture apparatus, cell images are captured periodically and stored.